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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-05-12 12:08:07 +0400
committerIngo Molnar <mingo@elte.hu>2011-05-20 01:25:29 +0400
commit80d02085d99039b3b7f3a73c8896226b0cb1ba07 (patch)
treec310902423ecb00effadcb59c60cbf118d4037cb /Documentation/RCU
parent11c476f31a0fabc6e604da5b09a6590b57c3fb20 (diff)
downloadlinux-80d02085d99039b3b7f3a73c8896226b0cb1ba07.tar.xz
Revert "rcu: Decrease memory-barrier usage based on semi-formal proof"
This reverts commit e59fb3120becfb36b22ddb8bd27d065d3cdca499. This reversion was due to (extreme) boot-time slowdowns on SPARC seen by Yinghai Lu and on x86 by Ingo . This is a non-trivial reversion due to intervening commits. Conflicts: Documentation/RCU/trace.txt kernel/rcutree.c Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/RCU')
-rw-r--r--Documentation/RCU/trace.txt17
1 files changed, 12 insertions, 5 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index 8173cec473aa..c078ad48f7a1 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -99,11 +99,18 @@ o "qp" indicates that RCU still expects a quiescent state from
o "dt" is the current value of the dyntick counter that is incremented
when entering or leaving dynticks idle state, either by the
- scheduler or by irq. This number is even if the CPU is in
- dyntick idle mode and odd otherwise. The number after the first
- "/" is the interrupt nesting depth when in dyntick-idle state,
- or one greater than the interrupt-nesting depth otherwise.
- The number after the second "/" is the NMI nesting depth.
+ scheduler or by irq. The number after the "/" is the interrupt
+ nesting depth when in dyntick-idle state, or one greater than
+ the interrupt-nesting depth otherwise.
+
+ This field is displayed only for CONFIG_NO_HZ kernels.
+
+o "dn" is the current value of the dyntick counter that is incremented
+ when entering or leaving dynticks idle state via NMI. If both
+ the "dt" and "dn" values are even, then this CPU is in dynticks
+ idle mode and may be ignored by RCU. If either of these two
+ counters is odd, then RCU must be alert to the possibility of
+ an RCU read-side critical section running on this CPU.
This field is displayed only for CONFIG_NO_HZ kernels.